<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    // 闰年：1.  能被4 整出不能被100整除  2. 能被400整除
    var year = parseInt( prompt('请输入您希望的年份') )

    if( (year % 4 === 0 && year % 100 !== 0) || year % 400 === 0) {
      console.log('这个年份是 闰年')
    } else {
      console.log('这个年份是 平年')
    }

  </script>
</body>
</html>